Since Apple began phasing out regular hard drives in favour of superior-yet-smaller-and-expensive SSD storage, MacBook owners have had to juggle their files in order to keep their machines from filling up. While cloud storage services help, those moments when you go off the grid can be a pain -- you don't really want to be lugging an external drive with you everywhere.
Transcend's JetDrive Lite SD cards are the most elegant solution I've seen. Available in 64GB and 128GB sizes, not only do they have impressive speeds (95MBs read, 60MBs write), they slip into your machine's SD card slot so perfectly you'd forget they were there at all. Sitting almost flush with a MacBook Air or MacBook Pro Retina's casing, you can leave them in at all times, bunging both into a rucksack without worrying that a protrusion will snap or cause damage to your precious data and laptop.
There's one important thing to remember when picking up the JetDrive Lite cards though, particularly if you have a 15-inch Retina MacBook Pro. You'll need to know exactly when your laptop launched before picking up a card, as they're built specifically to fit each different build. You can find out exactly which JetDrive Lite is compatible with your machine on the Transcend website.
Also, they're arguably a victim of their own sleek design -- once plugged in, the edges of the card sit so closely to the MacBook's casing that it can be a real struggle to remove the cards once popped inside. But being shock, water and dust resistant, at least the cards can withstand more abuse than your laptop can.
Available from Amazon, 128GB cards are priced at £64, and 64GB versions at £31.